1. Field of the Invention
This invention relates to circuits for controlling the operation of internal combustion engine ignition systems that utilize magnetos.
2. Prior Art
U.S. Pat. No. 3,726,265 to William A. Howard, the present inventor, discloses a safety interlock for magneto ignition engines and their related machines. The interlock circuit utilizes a first electronic control to short or ground the primary winding of the magneto when a transmission-operated switch indicates the transmission of an associated machine is in an unsafe condition for starting the engine. A second electronic control acts in conjunction with the switch when the transmission is in a safe condition for engine starting to prevent the first electronic control from shorting the ignition. Once the engine is running, a voltage-sensitive memory element prevents the first electronic control from shorting the ignition regardless of the condition of the transmission-operated switch. While this arrangement assured a safe start, continued operation was possible even if the operator left the vehicle. Additional prior art is referenced in the earlier Howard U.S. Pat. No. 3,726,265. A condition where the operator can leave a machine, such as riding lawn mower, while the transmission is in gear or the cutting blade is being powered by the engine is generally regarded as unsafe.